sorry to hear that mate, but all isnot lost,
my g.dad had one, quite a bad one, lost all mobilty down the left side, and although that was ahwile now, he still struggles a bit wioth his left arm.

however, as people go,he isnt very healthy (2 pachs of cigs a day for 65+ years etc) , and he was far older than 57, so, with my limited knowledge, i would say your dad has a top chance of returning almost fully to normal.

i hope he does mate, good luck with the futre